TL07 - Direct Head Measurments for Turbomachinery Design

Abstract

The isentropic head is one of the most important physical properties for the design and testing of compressors and turbines. It is a critical parameter for the determination of machinery work and power from test data and the associated equipment sizing or matching calculations. To determine enthalpy rise for a process, a path function between two thermodynamic states must be numerically integrated that includes at least three other thermodynamic gas properties such as density, specific heat, and speed of sound, and their derivatives. To address the high uncertainties in the determination of enthalpy change, and thus, head, a novel method and apparatus was developed for the direct measurement of this property. This paper describes the test apparatus and method that were developed for direct head measurements and demonstrates it using several gas mixture test cases. The results showed that the isentropic head could be measured for any gas and pressure/temperature state with an uncertainty of less than 0.5%. These test results for enthalpy rise can be used to improve existing equation of state prediction accuracy or directly input to the turbine or compressor design process for any specified application and operating condition.